Why cv_bridge uses OpenCV 3.2 in ROS Melodic?

Question

I have OpenCV 3.4 installed in Ubuntu 18. I also have installed ROS Melodic according to the website instructions. However, I keep on getting an error that libopencv_core.so.3.2 is required.

I already set my CMakeLists files to point to OpenCV 3.4. However, I found out that in the file:

/ros/melodic/share/cv_bridge/cmake/cv_bridgeConfig.cmake

there is the following line hardcoded in opencv3.2:

set(libraries "cv_bridge;/usr/lib/x86_64-linux-gnu/libopencv_core.so.3.2.0;/usr/lib/x86_64-linux-gnu/libopencv_imgproc.so.3.2.0;/usr/lib/x86_64-linux-gnu/libopencv_imgcodecs.so.3.2.0").

I tried to change it to 3.4 but I can not rebuild it.

The error I am getting is:

/opt/ros/melodic/lib/image_view/image_view: error while loading shared libraries: libopencv_core.so.3.2: cannot open shared object file: No such file or directory

Why is OpenCV 3.2 hardcoded in cv_bridge and how can I rebuild it with OpenCV 3.4?

Update: I eventually installed OpenCV 3.2 and it worked properly.

Answer 1

Because opencv development speed is much faster than ROS individual module. And a lot of ROS modules went depreciated after someone left the job.

But that's by no means the end of the day( maybe end of the day for noobs). You can build it directly with any version of opencv core function(besides imshow kind of function) others should perform just fine.

The easiest way is to do is: in the console before executing catkin_make try to execute the following

export CMAKE_PREFIX_PATH=/usr/local:$CMAKE_PREFIX_PATH
export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH

This should give preference to your custom OpenCV installation when doing the find_package(OpenCV 3.X.0 REQUIRED). Then compile and use the function of that version.

Well if you do have to use 3.4 then I think you have to build ros version of opencv and image transport and cvbridge to the 3.4 if that's what you are targeting.

You can find the link here https://github.com/ros-gbp/opencv3-release The highest they provide seems to be 3.3